Update: I decided to take the plunge over the weekend and install Windows 10 on an HP Stream 7 tablet. It had Windows 8.1 with Bing on it and I wasn't using it for very much of anything, and it was fully backed up, so I figured I had nothing to lose if things didn't work out with the switch to Windows 10.
So I downloaded the Media Creation Tool and ran it, choosing the option to update the machine I was working on, and let the process take its course. After nearly 2 hours, I was pleasantly surprised when it actually restarted and booted Windows 10 with all of my previous files and desktop programs still there. It was only at this point that I learned that Microsoft had pulled the Fall Update from their servers and what I had installed was the original July release with a bunch of updates.
The next day or so, I discovered that the Fall Update was again available for downloading, so I decided to go through the whole process again, having just configured my tablet the way I wanted it, including uninstalling a bunch of the useless bundled apps and changing several default programs to desktop apps I prefer to use.
Again, the process proceeded fairly smoothly and booted Windows 10 after about 90 minutes. At this point, I discovered that CCleaner had been uninstalled without notice (for supposed incompatibility), several bundled apps I had removed were reinstalled, and some of my default apps were changed back again to the bundled apps I had no intention of using.
Reinstalling CCleaner fixed the phantom incompatibility problem, and more time wasted reversing the installed/default apps situation restored my tablet to the way I had it initially.
I'll be using this tablet to test Windows 10 over the next few months. Hopefully Microsoft will sort out their procedures and stop changing settings and/or reinstalling deleted apps in future updates.
1You confirmed what steps I thought were going to be necessary for the update to work, which was useful to me. Thanks. – MikeFromMarkham – 2015-11-27T01:24:55.837